Lubricating gearing has always presented a problem, in particular when it is necessary to lubricate the meshing zone of a toothed wheel rotating at high speed.
A common solution consists in immersing the bottom portion of the wheel in a lubricant, generally oil. That solution is unsatisfactory since a large fraction of the lubricant used is ejected from the toothed periphery of the wheel under the effect of the centrifugal force associated with the wheel rotating, such that the quantity of lubricant in the meshing zone situated in the top portion of the wheel is small. In addition, it is necessary to have a large amount of lubricant so that the lubricant level is high and the bottom portion of the wheel is sufficiently immersed therein.
Another common solution consists in providing lubricant injectors, also referred to as nozzles, that are directed towards the meshing zone. That solution is also unsatisfactory since the jet of lubricant leaving the injectors generally ricochets off the teeth of the rotating wheel and only a small quantity of lubricant penetrates into the core of the meshing zone.
Another solution is described in document GB 1 355 156. That document proposes a system for gearing that comprises a toothed wheel mounted free on a shaft, the wheel being pierced by first channels that are fed with lubricant, the lubricant leaving those channels via orifices situated in the flanks of the teeth of the wheel. The first channels extend radially and have respective bends in the vicinity of their outlet orifices. The first channels are fed with lubricant via second channels that are connected to a pump. The second channels pass through the shaft axially and each of them has a bend prior to opening out into a groove formed in the periphery of the shaft.
A drawback of the system of GB 1 355 156 stems from the fact that the first and second channels are complex in shape and therefore difficult and expensive to make. In addition, the second channels need to pass axially along the shaft of the wheel. If the length of the shaft is considerable, the second channels are even more difficult and expensive to make. Furthermore, when making the first channels, there is a risk of damaging the flanks of the teeth. These flanks form part of the meshing interface or active profile of the set of teeth and their shape must be preserved. Finally, it is necessary for the wheels to turn relative to the shaft in order to ensure that all of the first channels are fed with lubricant.
Another solution is described in document U.S. Pat. No. 3,364,776. That document proposes a system for gearing comprising a toothed wheel mounted on a shaft, the wheel being pierced by channels fed with lubricant, the lubricant leaving the channels via outlet orifices present in the toothed periphery of the wheel. The inlet orifices of the channels are situated in the side face of the wheel. To feed the channels with lubricant, either the bottom portion of the wheel is immersed in a bath of lubricant (see FIG. 4 of U.S. Past. No. 3,364,776), thereby requiring a large amount of lubricant, or else a bowl-shaped cover is provided that is mounted on the side face of the wheel (see FIGS. 6 and 7 of U.S. Pat. No. 3,364,776). Fabricating and assembling the cover increases the number of parts in the system and its fabrication cost.